I get quite a few questions from designers along the lines of "How do I set the number of pss/hb *harmonics* and pnoise/hbnoise *sidebands* in order to get accurate results?" Here are some general guidelines that I follow:

*sidebands*(

*harmonics*) in the simulation can affect performance.

*pnoise/hbnoise*, the upper frequency to be considered for noise folding is set by the

*Maximum sideband*term. The number of

*Sidebands*that you specify corresponds to the set of periodic small signal output frequencies of interest. For instance, setting the

*Maximum sideband*lets you specify the number of frequency conversion terms to take into account.

**PSS shooting** takes 20 timepoints at the highest harmonic specified. In general, use 1/4 the number of harmonics as the number of sidebands. So, if you specify 7 *harmonics*, use up to 28 *sidebands*.. (There is a minimum of 200 points in the PSS analysis. You need 5 timepoints at the frequency of the highest sideband in the analysis).

If *maxsidebands* is less than 40, you shouldn't need to worry about increasing *harmonics*. If you have greater than 40 *sidebands*, either:

a. Set maxacfreq to the

number of sidebands*PSSfund

-- or --

b. Set the number of PSS

harmonicsto the number of pnoisesidebandsdivided by 4.As an example, say that you want 80

sidebands. Set the number ofharmonicsto 80/4=20 harmonics.

**PSS-HB and HB** analyzes such that only the harmonics specified are calculated. The pnoise *Maximum sideband* needs to be set to the same number as *harmonics* in the HB analysis. In MMSIM 7.2 and IC614isr2 or later, this is the default when the* Maximum sideband* field is left blank. Based on this, select a reasonable number of *harmonics* and *sidebands*, run your pss/pnoise (or hb/hbnoise) analysis. Then, increase your *harmonics/sidebands* and rerun the simulation. *If your pnoise or hbnoise answer changes, you need more harmonics/sidebands.*

To see more Solutions like this, log into Cadence Online Support at https://support.cadence.com/ .

Have fun simulating!

best regards,

Tawna Wilsey

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Useful.

Thanks Tawna, I have a question is that if I keep increasing the Maxsideband, the Pnoise is keeping increasing. Do you have any suggestions on how much the Maxsideband should be depending on circuit bandwidth etc.

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